(1) Field of the Invention
This invention relates to a method and apparatus for reading characters printed in magnetic ink which have a very weak magnetic field strength, with this invention utilizing magnetoresistive technology.
(2) Background Information
At the present time, MICR characters or those printed on documents in magnetic ink according to E13B and CMC 7 fonts, for example, have a magnetic field strength which is extremely weak. A poorly printed but still acceptable single printed bar in the CMC 7 font or coding, for example, may have a magnetic field strength of approximately 0.06Gauss. At the present time, such a weak magnetic field strength can be detected reliably only through using a read head which employs inductive technology.
There are several disadvantages in using an inductive type read head for reading MICR data on documents; they are:
1. The read head has a large number of coil turns therein, making the read head bulky and expensive to manufacture due to the manual or at best semi-automatic processes involved.
2. In order to obtain a satisfactory signal strength, it is necessary that there be high relative speed or velocity between the read head and the associated MICR characters on the document. In other words, the strength of the output signal is dependent upon the relative velocity mentioned. At the present time, about 400 inches per second is about the maximum feasible speed for moving a document past a stationary read head. At the slow end, a minimum of about 45 inches per second is what is needed to obtain a sufficient output for reading. At about 20 inches per second, the inductive type read head does not produce an output while using a practically feasible number of turns.
3. The physical size of the read head is bulky.
4. In order to achieve a good signal-to-noise ratio, it is necessary that the relative velocity between the read head and the MICR character be maintained at a high level.
With regard to prior art read heads which employed magnetoresistive technology, there was not enough signal strength developed for reading MICR data or characters from a document.